Curcumin is one of curcuminoids, which are main components of turmeric dyes that are obtainable from the roots and rhizomes of turmeric. Curcuminoids have been traditionally known as cholagogues, and it is also known that curcuminoids have, for example, tumorigenesis inhibitory effect, antioxidant effect, anti-inflammatory effect, hypocholesterolemic effect, anti-allergic effect, cerebral disease prophylactic effect, and cardiac disease prophylactic and therapeutic effects (Patent Literatures 1 and 2, and Non Patent Literatures 1 to 9). Since curcumin has such physiological activities, application of curcumin in, for example, pharmaceuticals, cosmetics, and nutritional supplementary foods has been considered.
However, curcumin has a problem that curcumin has low solubility in water and exhibits a low absorption rate when orally ingested. It has been reported that when a micronized curcuminoid is combined with gum ghatti in order to address the problem, oral absorbability is enhanced (Patent Literature 3).
Furthermore, it has also been reported that, for the purpose of improving photostability and coloring power of curcumin, a complex of curcumin with, for example, a water-soluble, branched or cyclic polysaccharide or a protein may be formed (Patent Literature 4).